Winter time is the the most “Yin”, time. The days get shorter, we start to live more in the dark literally, less sun time, especially if you are where I am in the northern hemisphere. The temperature outside gets colder, we want to retreat indoors, slow down, sleep more and drink warm drinks, even cozy up next to a fire or under a heated blanket to gain heat we are losing.
We go inside in a literal sense and a figurative sense.
We move inwards.